It is becoming general to mount an airbag device in a vehicle such as an automobile for absorbing impact on the occupant by inflating and deploying an airbag in the vehicle in case of an emergency such as a collision or sudden deceleration. A typical airbag device includes an airbag that is folded in a normal state and is inflated and deployed in case of an emergency, an inflator for supplying gas to the airbag, a retainer for fixing the airbag and the inflator, and an airbag cover that holds the retainer and forms an opening of the airbag.
In a collision or sudden deceleration of a vehicle, the inflator supplies gas to the airbag to inflate the airbag, causing the airbag to tear. Then, the airbag is released in the vehicle while inflating and deploying. Particularly in a passenger airbag device, an airbag is inflated and deployed in a space surrounded by an instrument panel, a windshield (front glass), and an occupant.
As described above, the airbag is released in the vehicle after tearing a fragile portion of the airbag cover during the process of inflation and deployment, and therefore, it sometimes suddenly pops out into the vehicle at the moment the airbag cover is torn. In this case, if the occupant is in proximity to the instrument panel, the airbag inflating and deploying at high speed interferes with the occupant, thereby making it difficult to softly restrain the occupant. In general, in view of this, a folding method for the air bag is devised to inflate the airbag as upward as possible in an early stage of deployment to avoid interference with the occupant in proximity to the instrument panel. However, such a conventional method has a problem in that the inflating direction may become unstable due to a subtle difference in the folding method of the airbag. As described in Japanese Unexamined Patent Application Publication No. 2001-334900, the invention has already been proposed in order to prevent the airbag inflating at high speed in an early stage of deployment from interfering with the occupant.
In the invention described in Japanese Unexamined Patent Application Publication No. 2001-334900, a ballooning control sheet arranged between a folded airbag and an inner surface of a lid, one end of the ballooning control sheet being fixed to a retainer, covers the folded airbag from a rear side of a vehicle body toward a front side of the vehicle body, wherein the ballooning control sheet has a total length longer than a reference length, and wherein the reference length is defined as a length of an arc of a circle having a center immediately above a first reference point and passing through the first reference point, the first reference point being at a rear end of the lid in the longitudinal direction of the vehicle body, the circle being tangent at the second reference point to a front glass, and the arc being between the first and the second reference points on the rear side of the vehicle body. According to such a structure, inflation of the airbag toward the rear side of the vehicle body in an early stage of deployment can be restricted by the ballooning control sheet, and early interference between the airbag and the occupant can be avoided.